The invention relates generally to non-aerosol, foam dispensing devices and particularly to a foam dispensing device which contains a separate air return system and which can be used in the inverted position.
Several patents have been issued for squeeze bottle type foam dispensing devices, in which foam is formed by mixing air and foamable liquid. Several of these devices are intended for use in the inverted condition and examples of such patents are U.S. Pat. No. 3,422,993, issued to G. L. Boehm and U.S. Pat. Nos. 3,709,437, 3,937,364 and 4,022,351 issued to H. E. Wright. In the Boehm patent no specific provision is made for the return of air into the unit. In two of the Wright patents namely U.S. Pat. Nos. 3,937,364 and 4,022,357 a valved air return system is disclosed in which a ball check valve is provided in the same conduit through which the formed foam is dispensed. In U.S. Pat. No. 4,022,351 an interior bag is used to entrap the air and keep it separate from the liquid. U.S. Pat. No. 3,622,049, issued to R. E. Thompson discloses a foaming device which has a separate air return but utilizes only a single dip tube.
In the case of the Boehm patent an air return into the inverted foam dispenser tends to cause foaming internally in the squeeze bottle container. The air return is slow and the unit tends to become inoperative after several squeezes because of the internal formation of foam which occupies the air space needed to produce foam.
In the Wright Patent, U.S. Pat. No. 3,937,364 the air return problem is solved to some extent. However, in order to produce an effective device the return tube must be of sufficient diameter to facilitate the flow of return air. A disadvantage of providing a relatively large diameter return air conduit is that liquid tends to migrate into the conduit when the foam dispensing device is stored in the upright position. The result is that when the unit is inverted for use the explusion of this liquid tends to create a "wet" shot. This problem is overcome in the Wright patent, U.S. Pat. No. 4,022,351 but requires the provision of an internal air bag.
The present invention solves these and other problems in a manner not disclosed in the known prior art.